Why does the tile overage default to 20%?

INDUSTRY STANDARD SUGGESTS ADDING AT LEAST 20% OVERAGE - Ordering at least 20% overage helps account for tile cuts, potential breakage, or future repairs. There is always the potential for breakage during moving and shipping tiles (2%-4%). We highly recommend having additional tiles for making tile cuts during your installation and to store for possible future plumbing (or other construction) repair needs. There is color variation for many of our tiles from batch to batch and within orders, so if you need more tiles in the future, it may not match your current tile.